1. Field of the Invention
This invention relates to inhalation activatable dispensers for use with aerosol containers which contain medicaments for inhalation therapy, are pressurized with liquid propellants, and include a metering valve through which a series of metered medicament doses can be dispensed. In particular the invention relates to inhalation activatable dispensers which do not require the patient to prime the dispenser by manually applying a load to the valve prior to or during use.
2. Description of the Related Art
Inhalation activatable dispensers for use with aerosol container assemblies of the type described above are known, their general purpose being to afford proper coordination of the dispensing of a dose of medicament with the inhalation of the patient thereby allowing the maximum proportion of the dose of medicament to be drawn into the patient's bronchial passages. Examples of such dispensers are described in British Patent Specification Nos. 1,269,554, 1,335,378, 1,392,192 and 2,061,116 and U.S. Pat. Nos. 3,456,644, 3,456,645, 3,456,646, 3,565,070, 3,598,294, 3,814,297, 3,605,738, 3,732,864, 3,636,949, 3,789,843 and 3,187,748 and German Patent No. 3,040,641.
European Patent No. 147028 discloses an inhalation activatable dispenser for use with an aerosol container in which a latch mechanism releasing vane is pivotally mounted in an air passage between an aerosol outlet valve and a mouthpiece, which latch mechanism cannot be released if force to activate the dispenser is not applied before a patient inhales.
The dispenser generally comprises a housing having a mouthpiece and an air passage therethrough terminating at the mouthpiece, the housing being adapted to receive an aerosol container and having a support block with a socket adapted to receive the stem of the valve of the aerosol container and a through orifice communicating between the socket and the air passage, and latch means having parts movable between an engaged position in which movement of the container and the support block toward each other upon the application of a force to bias the container and the support block toward each other is prevented and a release position in which movement of the container and the support block toward each other in response to said force is permitted causing the stem to move to its inner discharge position, the latch means comprising a vane mounted on the housing in the air passageway between the orifice and the mouthpiece for movement toward the mouthpiece under the influence of inhalation through the mouthpiece to release the latch means in which the vane moves toward the mouthpiece from a blocking to a nonblocking position with respect to the passageway in response to inhaling at the mouthpiece and releases the latch means only during the application of said force to bias the container and support block toward each other.
This inhalation device has been received favorably by patients and doctors since it not only overcomes the hand-lung coordination problem but it does so at a very low triggering flow rate (approximately 30 liters/minute) essentially silently, and with a very compact design barely larger than a standard inhaler. It is necessary to manually prime the inhalation device with a lever to apply the bias to the container prior to use.
U.S. Pat. No. 4,648,393 discloses an electrically-operated metered dose inhaler in which a mechanical valve blocking means is withdrawn by the action of a solenoid moving in response to the closing of a switch; the switch constitutes an electromechanical breath actuation means which responds to inhalation by the patient. The disclosed device relies entirely upon mechanical priming of the device by application of force to a spring.
WO87/04354 discloses a medical dosing device for the discharge of medicament for inhalation which comprises a handheld holder for a medicine container from which medicine is discharged via a valve into an air channel for inhalation by means of initiation of an activation device. The valve is operationally connected with a control unit arranged on initiation of the activation device to control the discharge valve for intermittent opening and closing repeatedly within an inhalation period. The control unit is an electronically controlled unit which activates an electrically controlled discharge valve.